Conventionally, solid oxide fuel cell (SOFC) devices were constituted so that during the startup process multiple processes for reforming fuel gas in a reformer, i.e. the partial oxidation reforming reaction process (POX process), auto thermal reforming reaction process (ATR process), and steam reforming reaction process (SR process) were passed through before transitioning to a generating process (see, for example, Patent Citation 1).
In an SOFC, the reformer, fuel cell stack, and the like disposed within a fuel cell module housing chamber can be caused to rise to an operating temperature by executing these processes in sequence.
The operating temperature in an SOFC is a high 600 to 800° C., and heat storage material is disposed around the fuel cell module housing chamber. Therefore this heat storage material can hold a large amount of heat during operation, raising thermal efficiency during operation.    Patent Citation 1: Published Unexamined Application 2004-319420